Arrangement with a helical spring and a support bearing for spring struts

ABSTRACT

A coil spring ( 1 ) and support bearing ( 2 ) arrangement for suspension struts ( 3 ) with a shock absorber, supporting a steering knuckle of an automobile has a rolling-contact bearing ( 7 ), with an axis (x); a receiving body ( 6 ), arranged below the rolling-contact bearing ( 7 ) in which the rolling-contact bearing is inserted; and a coil spring ( 1 ). The coil spring ( 1 ) has a force application line (f), which is offset relative to the axis (x) of the rolling-contact bearing ( 7 ) at an angle (a). The coil spring ( 1 ) has a first portion ( 8 ), which, starting from the winding end ( 17 ), winds around the receiving body ( 6 ). The first portion ( 8 ) abuts the receiving body ( 6 ). The winding end ( 17 ) of the coil spring ( 1 ) is arranged in the area of the plane E 1  formed by the force application line (f) and the axis (x). Thus, the axial forces acting from the coil spring ( 1 ) onto the rolling-contact bearing ( 7 ) have a maximum in the area of the force application line (f) of the transversal forces acting on the rolling-contact bearing ( 7 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the national phase filing of PCT Application SerialNo. PCT/EP00/12835 which claims priority to German Patent ApplicationNo. 100 04 121.3 filed Jan. 31, 2000, which applications are hereinexpressly incorporated by reference.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a coil spring and a support bearingarrangement for suspension struts, which support steering knuckels of anautomobile.

Suspension struts for automobiles have a shock absorber connected at itsupper end to the car body and at its lower end to the steering knuckle.A coil spring surrounds the shock absorber. The lower end of the coilspring is connected to the shock absorber via a coil spring seat. Asupport bearing, with a receiving body, receives the upper end windingof the coil spring. The support bearing is rigidly connected to thewinding. A rolling-contact bearing is connected to the receiving body onone side and is connected to the car body on the other side. Therolling-contact bearing enables rotation of the coil spring during thesteering movement of the wheels.

WO 89/05242 discloses a McPherson suspension strut which has a supportbearing with a receiving body connected to the support bearing and acoil spring. Here, the receiving body receives the bearing race on theside of the spring of the support bearing. The receiving body issupported by a multitude of ribs distributed over the front side of thereceiving body. The receiving body has formations corresponding to thespring against the end winding of the coil spring. The coil spring axisis arranged at an angle relative to the shock absorber axis.

DE 35 01 106 A1 discloses an arrangement with a support bearing and acoil spring for suspension struts. The winding diameter of the coilspring decreases in the upper area down to the mean diameter of thebearing mounted on the side of the car body. The coil spring elasticallysupports the piston rod of the shock absorber. Here, the axis of thecoil spring is inclined to the outside relative to the axis of the shockabsorber. This alignment enables a better transversal forcecompensation. The transversal forces are absorbed by the radial ballbearing.

In suspension struts, where the end winding of the coil spring issupported directly on a support bearing, the force application line ofthe coil spring is arranged at an angle relative to the axis of theshock absorber. In cases where the rolling-contact bearing, which ispart of the support bearing, is arranged centered on the axis of theshock absorber, the interplay between the radial and the axial forces inthe rolling-contact bearing is problematic. Due to the angled coilspring, radial forces also act on the rolling-contact bearing inaddition to the axial forces. Here, the axial forces are not constantover the circumference of the winding end of the coil spring. Due to themanufacturing tolerances, the axial forces have their maximum at thewinding end and between the winding end and the end of the abutment faceof the rolling-contact bearing or a minimum to the receiving body of thesupport bearing, respectively.

If the transversal force acting on the bearing, due to the coil springarranged at an angle relative to the shock absorber, is introduced suchthat no axial force is present in the area of the force application lineof the transversal force, the balls of the bearing are not held inposition in the groove bottom. The balls can run out of the groovebottom which results in a radial displacement of the two bearing races.Because of this, the sealing rings, into which the bearing races areinserted, can contact each other and an increased torque can beproduced. Again, the increased force can lead to a degradation of thesteering function and a reduction of the life time of the support.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a coil spring andsupport bearing arrangement for suspension struts supporting steeringknuckles, where the transmission of the force acting from the coilspring onto the support bearing is optimized when the force applicationline of the coil spring is offset relative to the axis of therolling-contact bearing of the support bearing.

A coil spring and a support bearing have a bearing centered on a firstaxis. A first receiving body is centered on the first axis and isarranged below the bearing and receives the bearing. A coil spring,having a force application line, is arranged at an angle relative to thefirst axis. An end winding of the coil spring at least partially windsaround the first insertion body. The end winding end faces therolling-contact bearing and has a winding end. The winding end lieswithin the area of a predetermined angle to a first plane. The angle isformed by the force application line and by the first axis. The firstplane represents the bisector of the angle.

In this embodiment, the axial forces, which pretension therolling-contact bearing to achieve a contact of the balls with thebearing races, have their maximum in the area of the force applicationline of the transversal force. This effectively prevents the balls ofthe rolling-contact bearing from run out off the grooves formed by thebearing races which, in turn, would lead to degradation of the bearingfunction and to reduction of the lifetime. Since the coil springdirectly abuts the receiving body, the construction is simplified, whichleads to a reduction of the manufacturing costs.

According to a further aspect of the present invention, the coil springhas a first portion which starts from the winding end. The first portionhas at least a constant radius over a predetermined winding angle aroundthe axis. The first portion of the coil spring is arranged in a secondplane perpendicular to the axis. The radius of the first portion of thecoil spring is approximated to the radius of the rolling-contactbearing. Because of this arrangement, the spring force can be directlyintroduced into the rolling-contact bearing without using additionalcomponents.

In accordance with the following aspect of the present invention, thecoil spring has a cranked second portion continuous with the firstportion of the end winding. The second portion increases the radius ofthe coil spring where the coil spring leaves the second plane. Becauseof the cranking of the coil spring, winding angles of the end windingaround the first receiving body or the rolling-contact bearing of 200°or more are achievable, respectively. Thus, the spring force can achievea uniform force distribution along a large winding angle onto therolling-contact bearing.

In a further embodiment, a damping body is arranged between the firstportion of the coil spring and the bearing receiving body. The dampingbody prevents transmission of vibration onto the car body of theautomobile, increasing driving comfort.

Preferably, the rolling-contact bearing is formed as an axialrolling-contact bearing or as an angular contact ball bearing.Generally, axial forces of the coil spring act on the rolling-contactbearing.

In a further preferred embodiment, the winding end is positioned in apredetermined angle bisected by the first plane, which is formed by theforce application line of the coil spring and the axis, and thepredetermined angle equals 30°. This has the advantage that the axialforces acting from the coil spring onto the rolling-contact bearing havetheir maximum in the area of the winding angle. Also, the transversalforces, resulting from the offsetting of the coil spring relative to theaxis, are acting in this area. Thus, the winding end is arranged on theside of the angle of attack of the force application line relative tothe first axis or on the side facing away from the angle of attack.

From the following detailed description, taken in conjunction with thedrawings and subjoined claims, other objects and advantages of thepresent invention will become apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a coil spring with an uppersupport bearing;

FIG. 2 is a longitudinal sectional view of the support bearing accordingto FIG. 1;

FIG. 3 is a diagram of the force distribution at the contact position ofthe coil spring with the rolling-contact bearing;

FIG. 4 is a plan view partially in section of a coil spring according toFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A coil spring 1 and an upper support bearing 2 arrangement for asuspension strut 3 of an automobile is shown in FIG. 1.

The upper end of the coil spring 1 is supported by a damping body 5, inthe form of a rubber backing. Also, a receiving body 6 on arolling-contact bearing 7, arranged on the side of the car body,supports the coil spring 1. The coil spring 1 is arranged on an axis(x). The force application line (f) of the coil spring is arranged at anangle (a) relative to the axis (x). The coil spring 1 is received in acoil spring seat 4 at its end facing the wheel axle. The coil springseat 4 is connected to a shock absorber.

As can be seen in FIG. 2, the rolling-contact bearing 7 is designed asan encapsulated axial grooved ball bearing. A cage 10 with balls 11 isarranged in the openings of the cage 10. Two bearing races 12, 13 areinserted into a lower sealing ring 14, and an upper sealing ring 15,respectively. The rolling-contact bearing 7 is guided between thereceiving body 6, on the lower side, and an attachment element 16, onthe upper side, to mount to the vehicle body to take up the axial andradial forces.

The receiving body 6 and the damping body 5 are formed sleeve-like inthe direction of the coil spring 1. The receiving body 6 and dampingbody 5 may be wound onto the coil spring 1. The radius (r) of the firstportion 8 of the coil spring 1, in which the coil spring winds aroundthe receiving body 6 or the damping body 5, respectively, around theangle (c) corresponds roughly to the radius of the rolling-contactbearing 7. The angle (c) may be 200° or more. This has the advantagethat the spring force F acts directly on the rolling-contact bearing 7.See FIG. 4.

The force transmission of the coil spring 1 into the receiving body 6and therefore, also into the rolling-contact bearing 7 is not constantover the first portion 8 of the coil spring 1 winding around thereceiving body 6. Rather, as shown in FIGS. 3 and 4, the maximum forcesare introduced at the winding end 17 and at the portion of the coilspring 1, in which the coil spring 1 still abuts the rolling-contactbearing 7 or the receiving body 6, respectively, before the coil spring1 leaves the second plane E₂. The axial pre-tension of therolling-contact bearing 7 is at a minimum in the area where the coilspring 1 discharges no axial force F₂ into the rolling-contact bearing7. Here, there is a danger that the transversal force F₁, resulting fromthe angle of attack of the coil spring 1 relative to the axis x of therolling-contact bearing 7 may force the bearing races 12, 13 to moveaway from each other.

In FIG. 3, the solid line shows the axial force F₂ acting on therolling-contact bearing over the winding angle (c) when the wheelsuspension is in a maximum rebound position. The dashed line defines theaxial force F₂ over the winding angle when the wheel suspension is in amaximum compression position (metal-to-metal position).

To prevent this movement, the coil spring 1 is arranged such that themaximum of the axial force F₂ acting on the rolling-contact bearing 7lies in the area of the force application line f₁ of the transversalforces F₁. This is achieved, as shown in FIG. 4, by arranging thewinding end 17 of the coil spring 1 within a predetermined angle (b)relative to the plane E₁. Plane E₁ is formed by the force applicationline (f) and the axis (x). Also, the plane E₁ bisects the predeterminedangle (b) which is equal to 30°. Here, the winding end 17 can bearranged on the side of the suspension strut 3 facing the angle ofattack of the force application line (f) relative to the axis (x) or onthe side facing away from the angle of attack.

The winding end 17 of the coil spring 1 is positioned in an area definedby the predetermined angle (b). The transversal force F₁ along the forceapplication line f₁ causes the balls 11 of the rolling-contact bearing 7in the area defined by the angle (b) to move. However, due to theespecially strong pretensioned force F₂ in the axial direction, theballs 11 remain in the groove bottom of the bearing races 12, 13. Thus,a radial displacement of the bearing races 12, 13 and also the sealingrings 14, 15 relative to each other, is prevented.

While the above detailed description describes the preferred embodimentof the present invention, the invention is susceptible to modification,variation and alteration without deviating from the scope and fairmeaning of the subjoined claims.

What is claimed is:
 1. A coil spring and a support bearing arrangementfor suspension struts, comprising: a rolling-contact bearing centered ona first axis; a first receiving body, centered on the first axis andarranged below the rolling-contact bearing, said first receiving bodyreceiving the rolling-contact bearing; a coil spring having a forceapplication line which is arranged at an angle to the first axis, afirst portion of said coil spring on an end facing the rolling-contactbearing, said first portion at least partially winds around the firstreceiving body and having a winding end, said winding end positionedwithin an area of a predetermined angle to a first plane, said firstplane formed by the force application line and by the first axis,wherein the first plane represents the bisector of the predeterminedangle.
 2. The arrangement according to claim 1, wherein the firstportion of the coil spring starting from the winding end has a radiuswhich is at least constant over a predetermined winding angle around theaxis.
 3. The arrangement according to claim 2, wherein the winding angleis larger than 200°.
 4. The arrangement according to claim 2, wherein aradius of the first portion of the coil spring is approximated to aradius of the rolling contact bearing.
 5. The arrangement according toclaim 1, wherein the first portion of the coil spring is arranged alongthe winding angle in a second plane arranged perpendicular to the axis.6. The arrangement according to claim 5, wherein the coil spring has acranked second portion continuous with the first portion, which enlargesa radius of the coil spring and in which the coil spring leaves thesecond plane.
 7. The arrangement according to claim 1, wherein a dampingbody is arranged between the first portion of the coil spring and thereceiving body.
 8. The arrangement according to claim 1, wherein therolling-contact bearing is designed as an axial rolling-contact bearingor as an angular contact ball bearing.
 9. The arrangement according toclaim 1, wherein said predetermined angle, in which the winding end ispositioned and which is bisected by the first plane, equals 30°.
 10. Thearrangement according to claim 1, wherein the winding end is arranged onthe side of the angle of attack of the force application line relativeto the first axis or on the side which is facing away from the angle ofattack.